A precision pointing system carrying a sensor, such as a telescope as its payload, may be susceptible to disturbances that produce structural vibrations and, consequently, pointing errors. Such vibrations may be attributed to mechanical components or assemblies, such as reaction wheel assemblies that are used as actuators in the precision pointing system. For the most part, because these systems tend not to have significant, inherent damping, these structural vibrations may degrade system performance and even cause structural fatigue over time.
To minimize the vibrations, an isolation strut is typically used to damp the structure and isolate the payload. One type of isolation strut operates as a three-parameter vibration isolation system and includes a hollow shaft, a piston, and a main spring. The piston receives vibration from the payload and is configured to slidably move through the shaft in response to the vibration. A flange extends radially from a midsection of the piston and has a top surface that is coupled to a first sealed bellows and a bottom surface that is coupled to a second sealed bellows. Each of the bellows has a chamber that is filled with fluid. Thus, when the piston moves axially through the shaft, fluid flows from one of the bellows chambers to the other. The shaft and piston are disposed within the main spring, which provides axial stiffness to the isolation strut in general.
During system operation, the isolation strut may be subjected to a frequency that causes the main spring to resonate. In some cases, the degree of resonance is such that it interferes with the capability of the strut to dampen vibrations. In other cases, the resonance may degrade the structural integrity of the spring, and the spring may become prematurely worn.
To attenuate the degree of resonance, one or more elastomer pads are typically contacted with or attached to the main spring. However, this configuration has drawbacks. For example, the elastomer pads unpredictably creep when exposed to certain temperatures, and thus, may not attenuate the resonance as desired. Additionally, the elastomer pads, which are typically made of insulating material, may block electrical and/or thermal conduction thereby creating electromagnetic interference and overheating issues.
Accordingly, it is desirable to have a vibration isolation apparatus that has improved damping capabilities. In addition, it is desirable to have a vibration isolation apparatus that does not resonate significantly when subjected to predetermined frequency ranges. Furthermore, other desirable features and characteristics of the present inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.